The present invention relates to silicone-containing compositions used to enhance shine or gloss in elastomeric surfaces. More particularly, this invention relates to an aqueous silicone-containing dispersion that contains less silicone but which results in comparable or higher shine or gloss when applied to elastomeric surfaces as compared to existing commercial formulations.
As mileage on a tire increases, the sidewall rubber surfaces often become dull and unattractive. Causes for this include, e.g., tire exposure to wind, weather, sunlight, scratching, abrasion from dirt, and other chemical and physical reactions. Prior art compositions which add gloss and restore tire appearance are disclosed, e.g., in U.S. Patent Application Publication No. 2004/0131787 (filed Nov. 23, 2003) to Fang and U.S. Patent Application Publication No. 2007/0010607 (filed Jun. 22, 2006) to Smith et al. In both of these patent applications to Fang and Smith, a compound other than a polyorganosiloxane is used in the composition to enhance gloss on an automotive tire. Fang's composition has a polyurethane component which is used to provide shine to tires. Smith's composition utilizes a polyalkene glycols or polyolefins to impart shine and gloss to tire.
Other prior art compositions for tire shine utilize siloxanes to increase gloss but they use levels of siloxane in excess of 10% and frequently greater than 20% of siloxanes to achieve desired levels of shine or gloss. Examples of references using high levels of siloxanes in tire shine compositions include: U.S. Pat. No. 5,693,704 to Estes; U.S. Pat. Nos. 6,206,956 and 6,221,433 (both to Muntz et al.); and U.S. Pat. No. 7,074,262 to Huang et al.
Given these limitations of the prior art, it is desirable to provide silicone compositions which can enhance the shine of elastomeric surfaces. In addition, the prior art references all teach that the application of tire shine compositions is done with an applicator of some kind to spread the gloss and make it appear uniform and to minimize the appearance of drips. By using a tire shine applicator much of the composition can be lost because it is retained in the absorbent applicator rather than on the treated surface. Therefore it is desirable to have a silicone composition for enhancing shine that may be sprayed on a surface in a uniform manner so that no direct touching with an applicator is necessary. It is also particularly desirable to provide silicone compositions which can enhance the shine of elastomeric surfaces while using a lower amount of silicone than commercial formulations.
It is also desirable to provide such compositions in the form of aqueous dispersions which are rheologically stable.
The use of emulsifying surfactants can pose problems relative to silicone emulsions that are used for cleaning, preserving and protecting surfaces. The level of emulsifying surfactant required in the compositions to produce storage stable emulsions are typically large in comparison to the level of surfactant required for cleaning action. Therefore, usually a substantial portion of the surfactant being used in the emulsion is merely for stability rather than for its role as a cleaning agent. Thus, some surfactant remains in the silicone phase deposited on the treated surface, resulting in undesirable characteristics both from an aesthetic and functional perspective, particularly since the surfactant employed is advantageously selected for its emulsifying capability rather than another benefit such as for wetting or cleaning purposes. Surfactant-based silicone emulsions used in surface treatment applications thus tend to suffer from undesirable characteristics, such as reduced shine, reduced coating longevity, increased susceptibility to hydration by water and/or high humidity, susceptibility to rinse-off by water, increased stickiness to the treated surface leading to dust pickup, retention of fingerprints and the like, owing to the surfactant employed as emulsifier.
Alternative approaches in the art for emulsifying silicone oils include the use of solvents and hydrotropes, alone and in combination with emulsifying surfactants, in order to achieve emulsification of the silicones. Solvents are not without their own issues, for instance, those that fall in the class of volatile organic compounds, are subject to ever increasing regulatory compliance issues. Since volatile solvents evaporate after application, the resulting films suffer less from the detrimental effects than formulations employing surfactant and emulsifiers to attain stability. However, in general, solvents are often flammable, aggressive to the substrates to which the silicone compositions are applied, require special packaging and handling requirements, and limit formulation options such as including other beneficial ingredients to the compositions that are not solvent compatible. Generally, high solvent and/or hydrotrope level and solvents and hydrotropes capable of coupling the silicone oil to water are required to achieve the emulsification of silicones. With high levels of solvent, similar detrimental effects occur in the formulations as in the formulations which rely on emulsifying surfactants, as described above.
Further, the prior art silicone emulsions achieve a high degree of stability with regards to storage conditions, temperature and time. However, the inherent stability of these emulsions can result in lowered performance due to the inability of the emulsions to break and release the emulsified silicone oils, at time of use so that the silicone oils are available to coat the intended target surface or substrate. It is desirable to coat or treat the surface with a layer of essentially pure silicone oil, or alternatively with silicone oil without significant or otherwise detrimental levels of emulsifying agents, rather than to provide a coating or layer of emulsified silicone oil with extraneous components present that not only do not contribute to the desired protective benefits, but may detract from these protective benefits.
To overcome some of the negative effects of the emulsifiers commonly employed, higher levels of the silicone oils are typically required for the formulations to exhibit the desired preserving, protecting and aesthetic benefits to treated surfaces such as those disclosed herein. In essence, a high silicone oil level, typically in amounts exceeding 20% by weight, and often greater than 30% by weight, are usually employed in practice to overcome the poorer performance of the prior art emulsions of silicone oils for these purposes.
Accordingly, there is a need in the art for improved water-based silicone dispersion compositions which will provide a beneficial cleaning, protecting, preserving and otherwise restorative effect to surfaces, as well as uniformly enhancing gloss or shine to a treated surface with low levels of silicone oils and without the need for extraneous emulsifying or solubilizing materials such as emulsifying surfactants, solvents or hydrotropes. In addition, there is a need for an improved-water based silicone dispersion which may be applied to surfaces by spraying which is self-leveling and will result in a uniform glossy coating which requires no touching or wiping of the treated surface.